An endoscopic telescope of this general type is familiar from patent DE 34 31 631 C2, FIG. 2, wherein rod lenses are alternately stacked with spacer tubes in a system tube. As can be known in principle from patent DE - AS 11 27 112, the stack can be held in restraint by spring loading between the end holding devices of the system tube.
In the design shown in the first referenced document, the exterior diameter of the rod lenses is smaller than the inside diameter of the system tube so as to reduce the danger of breaking the lenses when bending the tube. The exterior diameter of the spacer tubes also is usually chosen to be smaller than the inside diameter of the system tube as well, so that the spacer tubes, as also the lenses, can slide easily within the system tube. This facilitates assembly of the system and assures that the stack which is formed from the lenses and the spacer tubes will be securely held together by spring resistance in the axial direction so that the bedding of the tube lenses in the system tube is free from play.
In the event of shock (for example, shaking when the endoscope optics system falls down), the clearance between the system tube and the lenses that is necessarily present at the side results in a lateral tilting of the lenses which shall hereinafter be described as"skipping." This skipping gives rise to an unintended and detrimental change in the viewing direction.
In the familiar design referred to initially, the rod lenses are gripped at their ends by flanges jutting out in a line to the axis from the axial ends of the spacer tubes and revolving around their whole circumference so as to prevent any tilting of the tube lenses. A certain degree of assembly play has to be preserved even between these flanges and the rod lenses, however, so that a little skipping is still possible even in the case of this familiar design. Providing the spacer tubes with circumferential flanges, which requires work on a turning lathe, is very expensive, however, given the small size of the spacer tubes.